The work to date has indicated that immunization of mice against Coccidiodes immitis could be effected by extracts of spherules of C. immitis grown in vitro. We will study further the efficacy of such immunogenic extracts compared with whole spherules or spherule walls against more rigorous challenging doses of C. immitis. We will concentrate particularly on obtaining and testing extracts without the presence of contaminating exogenous enzymes, e.g. lysozyme, chitinase. It will be important to seek greater yields of spherules to provide sufficient material for extraction. In fact, we will also examine soluble materials released spontaneously during culture of the spherules in vitro for immunogenic activity. The nature (dry weight, chemical characteristics) will be studied to assess the relative potency of the extracts, and we will ascertain if the active material is soluble, particulate (but acellular) or both; and if it possesses the capacity to induce delayed hypersensitivity to coccidioidin and spherulin. BIBLIOGRAPHIC REFERENCE: Collins, M.S., D. Pappagianis, and J. Yee. Enzymatic solubilization of precipitin and complement fixing antigen from endospores, spherules and spherule fraction of Coccidioides immitis. Coccidioidomycosis: Current Clinical and Diagnostic Status. Libero Ajello, Ph.D. (Editor), Symposium Specialists, Miami, 1977.